I agree with Mermaid that when depressed it is often suppressed, certainly that is what I do. You need to recognise it and get support.
I suppressed it and it comes back and I cycle it over and over. Subjects we dwell on can hang around for years.
The thought patterns are not dealt with but hidden away I find. Then I take them out occasionally and beat myself up again. Once I recognise it and face it, it stops.
Recognising it yourself and having support would be good, but sometimes not possible if you are alone.
There are things that happen now which hurt us badly and we then cycle on them trying to find a solution. But there are also things in our past that we are stuck on and also form obstacles which prevent us from progressing in our lives. These issues stop us from attempting things (because we know we will fail). These problems we are dwelling on are holding us back, stopping the healing process, stopping us sleeping.
But this is not necessarily true.
I had things I was hung up on (when I was asked to look at this) from when I was 8 years old at school that meant I still avoided situations as I feel embarrassed. For no reason, only past hurt or injustice.
Earlier in this thread it was said that some professionals thought that depression could, over time allow the brain to learn and retain depressive thoughts. Probably true. This is what I describe from childhood, but not as severe as this MLC and affairs. This was something else, in a different league.
Recently I was introduced to a thing called EMT (Experience or event Modification Therapy).
It is quite emotionally painful process initially and reduced me to tears as I confronted things that were still painful that had happened to me as a child. The technique is impressive.
But this technique I learnt does the reverse of allowing your brain to keep these feelings, it allows you to process the negatives and play with them until they are positives. It modifies the event, trains your brain to overcome the negative and deals with your subconscious. You change what happened, like a play with a different script. You relive it in detail and change small elements each time you examine it until the event is now a pleasant one. It may take an hour to keep processing an event until it is completely positive.
This process if done correctly affects your subconscious. I suppose you have faced the event in detail and made it something nice.
Once your subconscious is modified....You literally dream away the problems.
Once you have taken each problem you identified in your list, as an event that needs to be modified and processed it, it is less of a problem.
The maximum events that an individual has listed is something like 14 events. You might only have 5 or 6.
It worked for me.
But I do think you can untrain your depression and recognise when it is affecting you. But it is a dark cave to be trapped in.
Life is good, once you understand.
We make our own happiness and everyone likes to be with happy people.
One man's junk is another's treasure and life goes on. Make yourself into a happy treasure. :-)